Canvas is an extremely heavy-duty plain-woven fabric used for making backpacks, fashionable handbags, and other functions where sturdiness is required. Canvas comes in two basic types: plain and duck. The threads in duck canvas are more tightly woven. Canvas is also classified in two ways: by weight (ounces per square yard) and by a graded number system. Our canvas bags are made out of natural unbleached (unless you ask for bleached) thicknesses ranging from (I've explained them in ounces per square yard)...